The present invention relates generally to trace gas detection and more specifically to cavity enhanced absorption spectroscopy systems and methods.
Optical absorption spectroscopy involves passing radiation through a sample, e.g., an analyte, an inferring properties of the sample from measurements performed on the radiation. For example, trace gas detection can be spectroscopically performed by taking measurements to detect the presence or absence of spectral absorption lines corresponding to the gas species of interest. Spectroscopic analysis of isotopes can also be performed. However, because the integral line intensities of absorption gas lines are sensitive to the gas temperature, and the pressure broadening of those lines is sensitive to the gas pressure and the gas composition, measurements of the isotopic ratio with high accuracy require measuring of the analyzed gas temperature and pressure with high accuracy, and measuring of the composition of major components of the analyzed gas. Moreover, because a measurement of the isotopic ratio very often requires working at low gas pressure, when gas absorption lines are narrow and their mutual overlapping decreased, it can be very hard to precisely measure the integral intensities of the absorption lines. Such measurements of the integral intensities require very precise measurements of laser frequency.
Accordingly it is desirable to provide improved spectroscopy systems and methods for measuring gas species and/or isotopes.